Automatic ignition and ionization detection circuit for gas tubes



m, 1970 w. B. F. HOGAN 3,539,863 AUTOMATIC IGNITION AND IONIZATIONDETECTION CIRCUIT FOR GAS TUBES I Filed April 11, 1967 Inventor WILLIAMB. E HOGAN ATTYS.

United States Patent 3,539,863- AUTOMATIC IGNITION AND IONIZATIONDETECTION CIRCUIT FOR GAS TUBES William B. F. Hogan, 36 Thomas St.,Oberlin, Ohio 44074 Filed Apr. 11, 1967, Ser. No. 646,438 (Filed underRule 47(1)) and 35 U.S.C. 118) Int. Cl. H05b 41/00 US. Cl. 315171 12Claims ABSTRACT OF THE DISCLOSURE A detecting circuit comprising adetecting switch in combination With a charging circuit and a gas tube.The detecting circuit also is responsive to ionization of the tube andis so disposed as to either maintain electrical pulses from the chargingcircuit to the tube or to inhibit the transmission of the pulses to thetube. The detecting switch comprises a switching device, an oscillator,and a control rectifier all acting in response to ignition ornonignition of the tube. If the tube ignites, detection occurs, adn theelectrical pulses cease. If the tube fails to ignite, the electricalpulses will continue being applied to the tube until ignition occurs.

This invention relates to the igniting of gas tubes as used inspectrophotometers and other commercial devices utilizing gas tubes andin particular to the automatic ignition of the tube by incorporating anionization detection circuit responsive to ionization of the gas tube.

Ignition of gas tubes as 'used in spectrophotometers and the likerequire the application of a charge or pulse of electrical energy acrossthe igniting terminals of the tube. Generally, the electrical potentialrequired to ignite the tube is greater than the potential required tokeep the tube in an operational state. The practice in igniting thesetubes has been to apply the electrical pulse or charge by manuallyturning a switch on and to visually observe the lamp or the instrumentwhich the lamp forms a part thereof, to see if ignition and thereforeionization has occurred. If ignition has indeed not occurred, which isvery common, it was required to repeat the procedure again untilignition occurred. This procedure is inefficient and very cumbersomedepending upon the particular device in which the tube is utilized andresults in a loss of man hours which is expensive.

The purpose of this invention is to provide an ionization detectingcircuit in which the charging circuit to the tube automaticallycontinues to transmit starting electrical pulses to the gas tube untilignition and therefor ionization has occurred. When an electrical pulseto the tube has ignited it and ionization has occurred, the detectingcircuit inhibits the further transmission of starting electrical pulsesto the gas tube so that only the necessary holding potential to keep thetube operating is applied.

This invention therfore replaces the existing inefficient manner inigniting the devices utilizing gas tubes with a time saving, efficientapparatus.

In the prior use of gas tubes, which are constant voltage devices, ithas been known to employ constant current circuits. More specifically, aresistive voltage divider circuit coupled to a differential amplifierhas been found to provide good current control for gas tubes. Thepresent invention employs such a current regulation circuit in a uniquemanner such that its input, which is a series coupling to one electrodeof the gas tube, controls a switch interposed between the currentregulation circuit and a charging circuit for the gas tube. In thismanner, prior to ignition of the gas tube, the combination coacts as aplural switched pulsing system and repeatedly applies ignition chargesor pulses to the gas tube. Once the gas tube ignites, the currentregulation circuit not only functions normally ,but also coacts with theremainder of the circuitry to disable the charging circuit.

Accordingly, it is a primary object of this invention to provide anautomatic circuit for detection of ionization of gas tubes.

It is a further object of this invention to provide a circuit for theautomatic firing of an electrical charge to the terminals of a gas tubeuntil ionization occurs.

It is still a further objective of this invention to provide a circuitwhich, upon ionization of a gas tube, inhibits further ignition chargesto be transmitted to the gas tube.

Yet another object of this invention is to employ the input of aconventional current regulation circuit for automatically detecting theignition state of a gas tube and for controlling an ignition chargingcircuit.

Other objects and advantages of the invention will become apparent froma consideration of the following specification, taken together with theaccompanying drawing which is a circuit diagram of the preferredembodiment of the invention.

The illustrated circuit will be discussed herein when a gas tube 10, isin a non-ionized state.

A positive potential 12 is applied to the plate 14 by lead 13 of thelamp 10. This potential is suitable to maintain ignition of the tube 10,once its ignition has occurred. In the preferred embodiment, thepotential 12 of +150 volts is adequate to maintain ignition of tube 10,which is a deuterium lamp.

The cathode 16, of the tube 10 is connected through a forward poleddiode 18 to the collector 20, of a detecting transistor 22. The emitter24 of the transistor 22 is connected to a grounded resistor 26 and tothe base 28 of a transistor 30 through a resistor 32. The base 28 isalso connected to a negative bias voltage 34 through a resistor 36 andto a grounded diode 38. The transistor 22 has a base 40 which isconnected to the collector 42 of the transistor 30, and is alsoconnected to a positive bias voltage 44, through a resistor 46. Aresistor 48 is also connected to the bias voltage 44 and in turn isconnected to the collector 50 of a transistor 52. The emitter 54 of thetransistor 52 is connected by a lead 55 to the emitter 56 of thetransistor 30 which are in turn connected to the bias voltage 34 througha resistor 58. The base 60 of the transistor 52 is connected to agrounded resistor 62.

A transistor 64 has a base 66 Which is connected to the collector 50 ofthe transistor 52 through a resistor 68 and is also connected to apositive bias voltage 70 through a forwardly poleddiode 72. The emitter73 of the transistor 64 is also connected to the bias voltage 70. Thecollector 74 of the transistor 64 is connected to the control electrode76 of a double base diode 78, through a resistor 80 and a lead 81. Agrounded capacitor 82, is also connected to the control electrode 76 ofthe double base diode 78 by lead 81 and to the resistor 80. The base 84of the double base diode 78 is also connected to the bias voltage 70through a resistor 86. The base 88 of the double base diode 78 isconnected to a grounded resistor 90 and to the control gate 92 of acontrol rectifier 94 by a lead 95. The control rectifier 94 having ananode 96, and a grounded cathode 110. The anode 96 of the controlrectifier 94 is connected through a resistor 98 and forwardly poleddiode 100' to a potential source 102 which in this embodiment is 300volts. The potential source 102 when combined with the potential source12 between the anode 14 and the cathode 16 of lamp 10, is sufficient toignite the lamp However, because of the inherent characteristics of thistype of lamp, which are well known in the art, ignition will not alwaysoccur, necessitating repeated application of the potential source 102 incombination with potential source 12, to the lamp 10, until ignitionoccurs. The anode 96 of the control rectifier 94 is connected to thecathode 16 of the lamp 10 through a capacitor 104 and a resistor 106 bythe common lead 108.

The elements of the illustrated circuit combined as herein describedestablish an automatic igniting and ionization detection circuit whichoperates in the manner next described.

The double base diode 78, as is well known in the art, has a highimpedance between its base 88 and its control electrode 76 and willretain such high impedance until a predetermined potential is applied tothe control electrode 76, whereupon, the high impedance drops to a lowvalue. The double base diode 78, connected to the capacitor 82 by thelead 81, forms an oscillator 78/ 82, as is well known in the art.

The transistors 52 and 30 are connected together to form a switchingcircuit 30/52, whereby when one transistor is on the other transistor is01f. In its normal state, that is when the lamp 10 is not ionized andthere is no current flow from the cathode 16 of the lamp 10 to thecollector 20 of the detecting transistor 22, the transistor 30 is 011and the transistor 52 is on. With the transistor 52 of the switchingcircuit 30/52 in the on condition, current flows from its collector 50through the resistor 68 to the base 66 of the transistor 64, which turnsthat transistor on. The transistor 64 is an on-ofi relay switch for theoscillator 78/ 82, which in the on condition causes a current to flowfrom its collector 74 to the capacitor 82 through the resistor 80.Thereupon, the capacitor 82 charges to the firing point of the doublebase diode 78. This firing point represents the predetermined value atwhich the high impedance between the control electrode 76 and the base88 breaks down, as discussed above. When the oscillators double basediode 78 fires, the resulting electrical pulse turns the controlrectifier 94 on and forces its anode 96 to ground. The anode 96 beingforced to ground through the cathode 110- of the control rectifier 94forces the charge on the charging capacitor 104 to the cathode 16 of thelamp 10. The charge transmitted from the charging capacitor 104, to thecathode of the lamp 10 is a negative 300 volts and when combined withthe potential 12, which is a positive 150 volts, results in a potentialof 450 volts between the anode 14 and the cathode 16 of the lamp 10. Thepotential source 102, the diode 100, the resistor 98 and the capacitor104 are connected together to form a charging circuit.

If the lamp 10 ignites, a current will flow from its cathode 16 to thecollector 20 of the detecting transistor 22. This current will in turnflow through transistor 22 and will turn off the transistor 52 and willturn on the transistor 30 of the switching circuit 30/52. When thetransistor 52 is off, there no longer is a current from the collector 50to the base 66 of the transistor 64, thereby turning off the transistor64. The capacitor 82 of the oscillator 78/82 will no longer charge whenthe transistor 64 is off and this in turn stops the oscillator 78/ 82,which therefore prevents any further charge on the capacitor 104 frombeing transmitted to the cathode 16 of the lamp 10.

If the lamp 10 did not ignite when the minus 300 volt charge wastransmitted from the charging capacitor 104 to its cathode 16, thecontrol rectifier 94 will turn off at the end of the pulse from thedouble base diode 78 which will be in the order of 10 to 20microseconds. The value of the resistor 98 has been selected so as notto provide a holding current for the control rectifier 94. Thetransistor 52 of the switching circuit 30/52 will remain on, as will thetransistor 64, thereby allowing the capacitor 82 to charge. Thetransmitting of the minus 300 volt signals from the capacitor 104 to thecathode 16 of the lamp 10 will continue until the lamp 10 is ignited.

The following values for the elements of the illustrated circuit setforth an operable apparatus as described above:

Element: Value or type Gas tube 10 Deuterium lamp. Potential 12 +150volts. Diode-18 600 volt, 500 mil. Transistor 22 DTS 423. Resistor 26 40ohms, 25 watts. Transistor 30 2N3569.

Resistor 32 1.1K ohms. Potential 34 15 volts. Resistor 36 1.47K ohms.Diode 38 600 volt, 500 mil. Potential 44 +50 volts. Resistor 46 1.8Kohms. Resistor 4+8 1.8K ohms. Transistor 52 2N3569. Resistor 58 6.8Kohms. Resistor 62 470 ohms. Transistor 64 2N36-38A. Resistor 68 3.3Kohms. Potential 70 +15 volts. Diode 72 600 volt, 500 mil. Double basediode 78 2-N1671. Resistor 80 120K ohms. Capacitor 82 22 microfarads.Resistor 86 100K ohms. Resistor 90 47 ohms. Control rectifier 94 2N3529.Resistor 98 22K ohms, 1 watt. Diode 100 600 volt, 500 mil. Potential 102+300 volts. Capacitor 104 2 microfarads, 200 volt. Resistor 106 15 ohms.

'Ignition of the lamp 10 is maintained by a constant current regulatingcircuit which is disposed between the cathode 16 of the lamp 10, and thetransistor 64 which acts as an on-off switch for the oscillator 78/82and the charging circuit as described above. The transistor 22 uponignition of the lamp 10 acts as a constant current supply. The emitter24 of the transistor 22 is directly connected to a resistive voltagedivider comprising resistors 26 and 32. The collector 20 of thetransistor 22 is connected to the cathode 16 of the lamp 10. Transistors30 and 5-2, after ionization of the lamp 10, act as a differentialamplifier with an output connected to transistor 64.

The constant current supply, the resistive voltage divider and thedifferential amplifier are connected together to form the constantcurrent regulating circuit between the cathode 16 of lamp 10 andtransistor 64, to provide current control for the lamp 10, after lamp 10ionizes.

Although a specific embodiment of the invention has been described andillustrated for use in a certain environment, it will be apparent tothose skilled in the art that the invention is capable of variousmodifications without departing from its spirit and scope.

What is sought to be secured by Letters Patent of the United States is:

1. An automatic ionization detecting circuit for a gas tube having atleast an anode and a cathode electrode comprising:

an ionization detecting switch including a transistor,

having an input serially coupled to one electrode of said gas tube, andtransistor enabling bias means,

a switching circuit connected to the output of said detecting switch,

an oscillator connected to be driven through said switching circuit,

an ionization charging circuit connected to one electrode of said gastube, and

a control rectifier connected between said charging circuit and saidoscillator and also connected to a source of ionizing potential,

said detecting circuit coacting to apply ionizing potential to oneelectrode of said gas tube until tube ionization is detected, to causesaid bias means to enable said transistor to inhibit said oscillator,and thereupon disconnecting the ionizing potential from said tube.

2. An ionization detecting circuit as set forth in claim 1 wherein saidoscillator comprises a capacitor and a diode, connected to receive anelectrical signal from said switching circuit and to transmit a gatingpulse to said control rectifier.

3. An ionization detecting circuit as set forth in claim 1, wherein saidcharging circuit comprises in series combination a connection to avoltage source, a diode, a resistor, a capacitor, and means to transmita stored electrical charge from said capacitor to one electrode of saidgas tube for initiating ionization thereof.

4. An ionization detecting circuit as set forth in claim 1 wherein saidcontrol rectifier comprises an anode coupled to said charging circuit,

a grounded cathode and a control gate,

said control gate being so disposed as to receive periodic controlsignals from said oscillator until ionization of said gas tube isdetected.

5. An automatic ionization detecting circuit for a gas tube having atleast an anode and a cathode electrode comprising:

an ionization detecting switch having an input serially coupled to oneelectrode of said gas tube,

a switching circuit connected to the output of said detecting switch andincluding two switches so connected and biased that when one is on theother is off, and output means in the form of a relay switch responsiveto one of said two switches,

an oscillator connected to be driven and controlled through the outputmeans of said switching circuit,

an ionization charging circuit connected to one electrode of said gastube, and

a control rectifier connected between said charging circuit and saidoscillator and also connected to a source of ionizing potential,

said detecting circuit coacting to apply ionizing potential to said gastube until tube ionization is detected and thereupon disconnecting theionizing potential from said tube.

6. An automatic ionization detecting circuit as set forth in claim 5-wherein a resistive voltage dividing circuit is coupled between saiddetecting switch and said switching circuit,

the combination thereof forming a current regulation circuit operativesubsequent to ionization and intfiuencing said relay switch andthereupon said oscillator for inhibiting said charging circuit fromapplying said ionizing potential to said gas tube.

7. An automatic ionization detecting circuit as set forth in claim 6wherein said two switches comprise two transistors having theirrespective emitters commonly connected and negatively biased,

one of said transistors has its collector connected to an input of saidrelay switch, and

a source of operating potential is coupled to the anode of said gas tubeand provides, only with said ionizing potential, suflicient potential toionize said tube.

8. An automatic ignition and ionization detection circuit comprising:

a gas diode tube having an anode and a cathode,

a first voltage source connected to the anode of said tube, said sourcebeing of sufficient potential to maintain ionization of said gas diode,but insuflicient for ignition thereof,

a deltaecting transistor connected to the cathode of said tu e,

a switching circuit comprising two transistors, one of said transistorsbeing connected to said detecting transistor,

an oscillator comprising a capacitor and a double base diode, saidcapacitor being connected to the second of said transistors of saidswitching circuit,

a control rectifier connected in. firing relation to one base electrodeof said double base diode, and

a charging circuit connected to said gas diode tube and comprising asecond voltage source of potential insufiicient by itself to ignite saidgas diode, and a capacitor resistively connected to both said secondsource and to the cathode of said gas diode and also connected to theanode of said control rectifier, the firing of said control rectifier bysaid oscillator enabling both said voltage sources to be applied to saidtube for ignition purposes.

9. An automatic ignition and ionization detection circult as set forthin claim '8 wherein circuit elements are connected to said detectingtransistor to inhibit its conduction prior to and during ignition ofsaid gas tube and to enable said detecting translstor upon ionization ofsaid gas tube to inhibit the firing of said control rectifier.

10. In a gas tube ignition system having a charging circuit for applyingpotential of a first magnltude to the gas tube,

a source for applying a lower operating potential during and subsequentto ignition, and

an ignition detector coupled between said tube and charging circuit andresponsive to tube ignition for decoupling said charging circuit fromsaid tube, the improvement which comprises:

the series combination of a switching circuit, a relay sw1tch, anoscillator, and a control rectifier coupled between said ignitiondetector and said charging clrcuit,

said control rectifier coupling to said charging circuit the potentialdiiference between said ignition and operating potentials and,

said difference being coupled to the cathode of said gas tube.

11. A system as defined in claim 10 further comprising:

a resistive voltage dividing circuit coupled between said ignitiondetector and said switching circuit,

the combination of said ignition detector, said voltage dividingcircuit, and said switching circuit forming a current regulation circuitoperative subsequent to ignition,

the operation of said current regulation circuit causing the operationof said relay switch for influencing said relay switch and thereuponsaid oscillator for inhibiting said charging circuit from applying saidpotential of a first magnitude to said gas tube.

12. An automatic ionization detecting circuit for a gas tube having atleast an anode and a cathode comprising: an ionization detecting switchhaving an input serially coupled to a unidirectional conduit from saidgas tube cathode for receiving an enabling signal in response toionization of said tube,

a switching circuit connected to the output of said detecting switch,

an oscillator connected to be driven through said switching circuit,

an ionization charging circuit connected to said gas tube cathode, and

7 8 a control rectifier connected between said charging cir- 3,122,6762/ 1964 Kind 315--174 cuit and said oscillator and also connected to asource 3,222,570 12/ 1965 Clark et al 315241 of ionizing potential,3,280,368 10/1966 Ahmed et al 315173 said detecting circuit coacting toapply ionizing poten- 3,305,734 2/1967 Buttenhofi 307-401 tial to saidcathode until tube ionization is detected 5 and thereupon disconnectingthe ionizing potential JERRY CRAIG, Pflmary EXamll'lel from said tube.

US. Cl. X.R.

References Cited 315-176, 225, 240; 307-452 UNITED STATES PATENTS 103,115,593 12/1963 Hauer 315--200

